Types of microscope devices include a super-resolution microscope, which enables observation with a resolution higher than the limit of resolution of optical systems. One form of the super-resolution microscope is known as a structured illumination microscope (SIM), which is configured to illuminate a sample with structured illumination to acquire modulated images, and demodulate the modulated images to generate a super-resolution image of the sample (see, for example, Patent Literature 1). This method involves branching a beam that has been emitted from a light source into a plurality of beams with a diffraction grating or the like, and illuminating a sample with interference fringes formed by causing the beams to interfere with each other in the vicinity of the sample, thereby acquiring modulated images of the sample.